This invention relates to a process for altering the color of hair that has been dyed with dihydroxyindole, or a metal catalyzed dihydroxyindole system (hereinafter collectively referred to as DHI), by treating the dyed hair with an acidic solution.
Dyeing hair with DHI has many advantages: DHI produces intense haircolor, it is a relatively mild hair treatment that does not damage hair, and it is a precursor to a natural pigment, melanin--a characteristic that pleases consumers. The primary disadvantage of using DHI to dye hair is its inability to produce colors other than gray or black. Most natural haircolors are warmer, redder shades than those produced using DHI. Hence, there exists a need in the art for obtaining natural-looking haircolors using DHI dyes.
There have been a number of attempts to obtain such haircolors with DHI dyes. French Patent Application 2 657 781 (Richard) discloses a method for removing or lightening the color of DHI-dyed hair that comprises first applying a potassium permanganate solution to DHI-dyed hair and then applying a reducing agent (sodium bisulfate, sodium hydrosulfate, oxalic acid, thioglycolic acid, citric acid, or ascorbic acid). However, the haircolors produced with that method are due at least in part to the deposition of manganese dioxide on the hair. Manganese dioxide is a colorant that masks the color produced by DHI treatment. Thus it was surprising that the present invention, using an acidic solution (which may be a reducing agent) without an added colorant and absent the presence in the acidic solution of other color modifiers such as hydrogen perioxide, periodic acid and its salts, sodium hypochlorite, nitrites and the like, alone or in admixture, produces natural-looking haircolor without needing to mask the color of the DHI-dyed hair. Furthermore, permanganate is a cosmetically unacceptable colorant. It forms an intensely colored solution that stains easily and thus is very difficult to work with. In contrast, the claimed process is simple and harmless.
U.S. Pat. No. 3,194,734 (Seemuller et al.) discloses a process and composition that produce warm, natural haircolor shades by using methyl derivatives of DHI and an oxidizing agent.
U.S. Pat. No. 4,822,375 (Lang et al.) discloses a process and composition that produce warm, natural haircolor shades by using DHI derivatives.
U.S. Pat. No. 5,011,500 (Grollier et al.) discloses a process and composition that produce warm, natural haircolor shades by using indole derivatives combined with synthetic dye materials such as nitro dyes.
U.S. Pat. No. 5,021,067 (Grollier) discloses a process and composition that produce warm, natural haircolor shades by using DHI with at least one para-phenylenediamine (a synthetic dye material) disubstituted on one of the amino groups.
U.S. Pat. No. 5,053,053 (De Labbey et al.) discloses a process and a kit that produce warm, natural haircolor shades by using DHI with at least one quinone derivative (a synthetic dye material).